The discussion of Definitions falls into five parts. For you have to show
either (1) that it is not true at all to apply the expression as well to
that to which the term is applied (for the definition of Man ought to be
true of every man); or (2) that though the object has a genus, he has failed
to put the object defined into the genus, or to put it into the appropriate
genus (for the framer of a definition should first place the object in
its genus, and then append its differences: for of all the elements of
the definition the genus is usually supposed to be the principal mark of
the essence of what is defined): or (3) that the expression is not peculiar
to the object (for, as we said above as well, a definition ought to be
peculiar): or else (4) see if, though he has observed all the aforesaid
cautions, he has yet failed to define the object, that is, to express its
essence. (5) It remains, apart from the foregoing, to see if he has defined
it, but defined it incorrectly.

Whether, then, the expression be not also true of that of which
the term is true you should proceed to examine according to the commonplace
rules that relate to Accident. For there too the question is always 'Is
so and so true or untrue?': for whenever we argue that an accident belongs,
we declare it to be true, while whenever we argue that it does not belong,
we declare it to be untrue. If, again, he has failed to place the object
in the appropriate genus, or if the expression be not peculiar to the object,
we must go on to examine the case according to the commonplace rules that
relate to genus and property.

It remains, then, to prescribe how to investigate whether the object
has been either not defined at all, or else defined incorrectly. First,
then, we must proceed to examine if it has been defined incorrectly: for
with anything it is easier to do it than to do it correctly. Clearly, then,
more mistakes are made in the latter task on account of its greater difficulty.
Accordingly the attack becomes easier in the latter case than in the
former.

Incorrectness falls into two branches: (1) first, the use of obscure
language (for the language of a definition ought to be the very clearest
possible, seeing that the whole purpose of rendering it is to make something
known); (secondly, if the expression used be longer than is necessary:
for all additional matter in a definition is superfluous. Again, each of
the aforesaid branches is divided into a number of others.

Part 2

One commonplace rule, then, in regard to obscurity is, See if the
meaning intended by the definition involves an ambiguity with any other,
e.g. 'Becoming is a passage into being', or 'Health is the balance of hot
and cold elements'. Here 'passage' and 'balance' are ambiguous terms: it
is accordingly not clear which of the several possible senses of the term
he intends to convey. Likewise also, if the term defined be used in different
senses and he has spoken without distinguishing between them: for then
it is not clear to which of them the definition rendered applies, and one
can then bring a captious objection on the ground that the definition does
not apply to all the things whose definition he has rendered: and this
kind of thing is particularly easy in the case where the definer does not
see the ambiguity of his terms. Or, again, the questioner may himself distinguish
the various senses of the term rendered in the definition, and then institute
his argument against each: for if the expression used be not adequate to
the subject in any of its senses, it is clear that he cannot have defined
it in any sense aright.

Another rule is, See if he has used a metaphorical expression,
as, for instance, if he has defined knowledge as 'unsupplantable', or the
earth as a 'nurse', or temperance as a 'harmony'. For a metaphorical expression
is always obscure. It is possible, also, to argue sophistically against
the user of a metaphorical expression as though he had used it in its literal
sense: for the definition stated will not apply to the term defined, e.g.
in the case of temperance: for harmony is always found between notes. Moreover,
if harmony be the genus of temperance, then the same object will occur
in two genera of which neither contains the other: for harmony does not
contain virtue, nor virtue harmony. Again, see if he uses terms that are
unfamiliar, as when Plato describes the eye as 'brow-shaded', or a certain
spider as poison-fanged', or the marrow as 'boneformed'. For an unusual
phrase is always obscure.

Sometimes a phrase is used neither ambiguously, nor yet metaphorically,
nor yet literally, as when the law is said to be the 'measure' or 'image'
of the things that are by nature just. Such phrases are worse than metaphor;
for the latter does make its meaning to some extent clear because of the
likeness involved; for those who use metaphors do so always in view of
some likeness: whereas this kind of phrase makes nothing clear; for there
is no likeness to justify the description 'measure' or 'image', as applied
to the law, nor is the law ordinarily so called in a literal sense. So
then, if a man says that the law is literally a 'measure' or an 'image',
he speaks falsely: for an image is something produced by imitation, and
this is not found in the case of the law. If, on the other hand, he does
not mean the term literally, it is clear that he has used an unclear expression,
and one that is worse than any sort of metaphorical
expression.

Moreover, see if from the expression used the definition of the
contrary be not clear; for definitions that have been correctly rendered
also indicate their contraries as well. Or, again, see if, when it is merely
stated by itself, it is not evident what it defines: just as in the works
of the old painters, unless there were an inscription, the figures used
to be unrecognizable.

Part 3If, then, the definition be not clear, you should proceed to examine
on lines such as these. If, on the other hand, he has phrased the definition
redundantly, first of all look and see whether he has used any attribute
that belongs universally, either to real objects in general, or to all
that fall under the same genus as the object defined: for the mention of
this is sure to be redundant. For the genus ought to divide the object
from things in general, and the differentia from any of the things contained
in the same genus. Now any term that belongs to everything separates off
the given object from absolutely nothing, while any that belongs to all
the things that fall under the same genus does not separate it off from
the things contained in the same genus. Any addition, then, of that kind
will be pointless.

Or see if, though the additional matter may be peculiar to the
given term, yet even when it is struck out the rest of the expression too
is peculiar and makes clear the essence of the term. Thus, in the definition
of man, the addition 'capable of receiving knowledge' is superfluous; for
strike it out, and still the expression is peculiar and makes clear his
essence. Speaking generally, everything is superfluous upon whose removal
the remainder still makes the term that is being defined clear. Such, for
instance, would also be the definition of the soul, assuming it to be stated
as a 'self-moving number'; for the soul is just 'the self-moving', as Plato
defined it. Or perhaps the expression used, though appropriate, yet does
not declare the essence, if the word 'number' be eliminated. Which of the
two is the real state of the case it is difficult to determine clearly:
the right way to treat the matter in all cases is to be guided by convenience.
Thus (e.g.) it is said that the definition of phlegm is the 'undigested
moisture that comes first off food'. Here the addition of the word 'undigested'
is superfluous, seeing that 'the first' is one and not many, so that even
when undigested' is left out the definition will still be peculiar to the
subject: for it is impossible that both phlegm and also something else
should both be the first to arise from the food. Or perhaps the phlegm
is not absolutely the first thing to come off the food, but only the first
of the undigested matters, so that the addition 'undigested' is required;
for stated the other way the definition would not be true unless the phlegm
comes first of all.

Moreover, see if anything contained in the definition fails to
apply to everything that falls under the same species: for this sort of
definition is worse than those which include an attribute belonging to
all things universally. For in that case, if the remainder of the expression
be peculiar, the whole too will be peculiar: for absolutely always, if
to something peculiar anything whatever that is true be added, the whole
too becomes peculiar. Whereas if any part of the expression do not apply
to everything that falls under the same species, it is impossible that
the expression as a whole should be peculiar: for it will not be predicated
convertibly with the object; e.g. 'a walking biped animal six feet high':
for an expression of that kind is not predicated convertibly with the term,
because the attribute 'six feet high' does not belong to everything that
falls under the same species.

Again, see if he has said the same thing more than once, saying
(e.g.) 'desire' is a 'conation for the pleasant'. For 'desire' is always
'for the pleasant', so that what is the same as desire will also be 'for
the pleasant'. Accordingly our definition of desire becomes 'conation-for-the-pleasant':
for the word 'desire' is the exact equivalent of the words 'conation for-the-pleasant',
so that both alike will be 'for the pleasant'. Or perhaps there is no absurdity
in this; for consider this instance:-Man is a biped': therefore, what is
the same as man is a biped: but 'a walking biped animal' is the same as
man, and therefore walking biped animal is a biped'. But this involves
no real absurdity. For 'biped' is not a predicate of 'walking animal':
if it were, then we should certainly have 'biped' predicated twice of the
same thing; but as a matter of fact the subject said to be a biped is'a
walking biped animal', so that the word 'biped' is only used as a predicate
once. Likewise also in the case of 'desire' as well: for it is not 'conation'
that is said to be 'for the pleasant', but rather the whole idea, so that
there too the predication is only made once. Absurdity results, not when
the same word is uttered twice, but when the same thing is more than once
predicated of a subject; e.g. if he says, like Xenocrates, that wisdom
defines and contemplates reality:' for definition is a certain type of
contemplation, so that by adding the words 'and contemplates' over again
he says the same thing twice over. Likewise, too, those fail who say that
'cooling' is 'the privation of natural heat'. For all privation is a privation
of some natural attribute, so that the addition of the word 'natural' is
superfluous: it would have been enough to say 'privation of heat', for
the word 'privation' shows of itself that the heat meant is natural
heat.

Again, see if a universal have been mentioned and then a particular
case of it be added as well, e.g. 'Equity is a remission of what is expedient
and just'; for what is just is a branch of what is expedient and is therefore
included in the latter term: its mention is therefore redundant, an addition
of the particular after the universal has been already stated. So also,
if he defines 'medicine' as 'knowledge of what makes for health in animals
and men', or 'the law' as 'the image of what is by nature noble and just';
for what is just is a branch of what is noble, so that he says the same
thing more than once.

Part 4

Whether, then, a man defines a thing correctly or incorrectly you
should proceed to examine on these and similar lines. But whether he has
mentioned and defined its essence or no, should be examined as follows:
First of all, see if he has failed to make the definition through terms
that are prior and more intelligible. For the reason why the definition
is rendered is to make known the term stated, and we make things known
by taking not any random terms, but such as are prior and more intelligible,
as is done in demonstrations (for so it is with all teaching and learning);
accordingly, it is clear that a man who does not define through terms of
this kind has not defined at all. Otherwise, there will be more than one
definition of the same thing: for clearly he who defines through terms
that are prior and more intelligible has also framed a definition, and
a better one, so that both would then be definitions of the same object.
This sort of view, however, does not generally find acceptance: for of
each real object the essence is single: if, then, there are to be a number
of definitions of the same thing, the essence of the object will be the
same as it is represented to be in each of the definitions, and these representations
are not the same, inasmuch as the definitions are different. Clearly, then,
any one who has not defined a thing through terms that are prior and more
intelligible has not defined it at all.

The statement that a definition has not been made through more
intelligible terms may be understood in two senses, either supposing that
its terms are absolutely less intelligible, or supposing that they are
less intelligible to us: for either sense is possible. Thus absolutely
the prior is more intelligible than the posterior, a point, for instance,
than a line, a line than a plane, and a plane than a solid; just as also
a unit is more intelligible than a number; for it is the prius and starting-point
of all number. Likewise, also, a letter is more intelligible than a syllable.
Whereas to us it sometimes happens that the converse is the case: for the
solid falls under perception most of all-more than a plane-and a plane
more than a line, and a line more than a point; for most people learn things
like the former earlier than the latter; for any ordinary intelligence
can grasp them, whereas the others require an exact and exceptional
understanding.

Absolutely, then, it is better to try to make what is posterior
known through what is prior, inasmuch as such a way of procedure is more
scientific. Of course, in dealing with persons who cannot recognize things
through terms of that kind, it may perhaps be necessary to frame the expression
through terms that are intelligible to them. Among definitions of this
kind are those of a point, a line, and a plane, all of which explain the
prior by the posterior; for they say that a point is the limit of a line,
a line of a plane, a plane of a solid. One must, however, not fail to observe
that those who define in this way cannot show the essential nature of the
term they define, unless it so happens that the same thing is more intelligible
both to us and also absolutely, since a correct definition must define
a thing through its genus and its differentiae, and these belong to the
order of things which are absolutely more intelligible than, and prior
to, the species. For annul the genus and differentia, and the species too
is annulled, so that these are prior to the species. They are also more
intelligible; for if the species be known, the genus and differentia must
of necessity be known as well (for any one who knows what a man is knows
also what 'animal' and 'walking' are), whereas if the genus or the differentia
be known it does not follow of necessity that the species is known as well:
thus the species is less intelligible. Moreover, those who say that such
definitions, viz. those which proceed from what is intelligible to this,
that, or the other man, are really and truly definitions, will have to
say that there are several definitions of one and the same thing. For,
as it happens, different things are more intelligible to different people,
not the same things to all; and so a different definition would have to
be rendered to each several person, if the definition is to be constructed
from what is more intelligible to particular individuals. Moreover, to
the same people different things are more intelligible at different times;
first of all the objects of sense; then, as they become more sharpwitted,
the converse; so that those who hold that a definition ought to be rendered
through what is more intelligible to particular individuals would not have
to render the same definition at all times even to the same person. It
is clear, then, that the right way to define is not through terms of that
kind, but through what is absolutely more intelligible: for only in this
way could the definition come always to be one and the same. Perhaps, also,
what is absolutely intelligible is what is intelligible, not to all, but
to those who are in a sound state of understanding, just as what is absolutely
healthy is what is healthy to those in a sound state of body. All such
points as this ought to be made very precise, and made use of in the course
of discussion as occasion requires. The demolition of a definition will
most surely win a general approval if the definer happens to have framed
his expression neither from what is absolutely more intelligible nor yet
from what is so to us.

One form, then, of the failure to work through more intelligible
terms is the exhibition of the prior through the posterior, as we remarked
before.' Another form occurs if we find that the definition has been rendered
of what is at rest and definite through what is indefinite and in motion:
for what is still and definite is prior to what is indefinite and in
motion.

Of the failure to use terms that are prior there are three
forms:
(1) The first is when an opposite has been defined through its opposite,
e.g.i. good through evil: for opposites are always simultaneous by nature.
Some people think, also, that both are objects of the same science, so
that the one is not even more intelligible than the other. One must, however,
observe that it is perhaps not possible to define some things in any other
way, e.g. the double without the half, and all the terms that are essentially
relative: for in all such cases the essential being is the same as a certain
relation to something, so that it is impossible to understand the one term
without the other, and accordingly in the definition of the one the other
too must be embraced. One ought to learn up all such points as these, and
use them as occasion may seem to require.

(2) Another is-if he has used the term defined itself. This passes
unobserved when the actual name of the object is not used, e.g. supposing
any one had defined the sun as a star that appears by day'. For in bringing
in 'day' he brings in the sun. To detect errors of this sort, exchange
the word for its definition, e.g. the definition of 'day' as the 'passage
of the sun over the earth'. Clearly, whoever has said 'the passage of the
sun over the earth' has said 'the sun', so that in bringing in the 'day'
he has brought in the sun.

(3) Again, see if he has defined one coordinate member of a division
by another, e.g. 'an odd number' as 'that which is greater by one than
an even number'. For the co-ordinate members of a division that are derived
from the same genus are simultaneous by nature and 'odd' and 'even' are
such terms: for both are differentiae of number.

Likewise also, see if he has defined a superior through a subordinate
term, e.g. 'An "even number" is "a number divisible into halves"', or '"the
good" is a "state of virtue" '. For 'half' is derived from 'two', and 'two'
is an even number: virtue also is a kind of good, so that the latter terms
are subordinate to the former. Moreover, in using the subordinate term
one is bound to use the other as well: for whoever employs the term 'virtue'
employs the term 'good', seeing that virtue is a certain kind of good:
likewise, also, whoever employs the term 'half' employs the term 'even',
for to be 'divided in half' means to be divided into two, and two is
even.

Part 5

Generally speaking, then, one commonplace rule relates to the failure
to frame the expression by means of terms that are prior and more intelligible:
and of this the subdivisions are those specified above. A second is, see
whether, though the object is in a genus, it has not been placed in a genus.
This sort of error is always found where the essence of the object does
not stand first in the expression, e.g. the definition of 'body' as 'that
which has three dimensions', or the definition of 'man', supposing any
one to give it, as 'that which knows how to count': for it is not stated
what it is that has three dimensions, or what it is that knows how to count:
whereas the genus is meant to indicate just this, and is submitted first
of the terms in the definition.

Moreover, see if, while the term to be defined is used in relation
to many things, he has failed to render it in relation to all of them;
as (e.g.) if he define 'grammar' as the 'knowledge how to write from dictation':
for he ought also to say that it is a knowledge how to read as well. For
in rendering it as 'knowledge of writing' has no more defined it than by
rendering it as 'knowledge of reading': neither in fact has succeeded,
but only he who mentions both these things, since it is impossible that
there should be more than one definition of the same thing. It is only,
however, in some cases that what has been said corresponds to the actual
state of things: in some it does not, e.g. all those terms which are not
used essentially in relation to both things: as medicine is said to deal
with the production of disease and health; for it is said essentially to
do the latter, but the former only by accident: for it is absolutely alien
to medicine to produce disease. Here, then, the man who renders medicine
as relative to both of these things has not defined it any better than
he who mentions the one only. In fact he has done it perhaps worse, for
any one else besides the doctor is capable of producing
disease.

Moreover, in a case where the term to be defined is used in relation
to several things, see if he has rendered it as relative to the worse rather
than to the better; for every form of knowledge and potentiality is generally
thought to be relative to the best.

Again, if the thing in question be not placed in its own proper
genus, one must examine it according to the elementary rules in regard
to genera, as has been said before.'

Moreover, see if he uses language which transgresses the genera
of the things he defines, defining, e.g. justice as a 'state that produces
equality' or 'distributes what is equal': for by defining it so he passes
outside the sphere of virtue, and so by leaving out the genus of justice
he fails to express its essence: for the essence of a thing must in each
case bring in its genus. It is the same thing if the object be not put
into its nearest genus; for the man who puts it into the nearest one has
stated all the higher genera, seeing that all the higher genera are predicated
of the lower. Either, then, it ought to be put into its nearest genus,
or else to the higher genus all the differentiae ought to be appended whereby
the nearest genus is defined. For then he would not have left out anything:
but would merely have mentioned the subordinate genus by an expression
instead of by name. On the other hand, he who mentions merely the higher
genus by itself, does not state the subordinate genus as well: in saying
'plant' a man does not specify 'a tree'.

Part 6

Again, in regard to the differentiae, we must examine in like manner
whether the differentiae, too, that he has stated be those of the genus.
For if a man has not defined the object by the differentiae peculiar to
it, or has mentioned something such as is utterly incapable of being a
differentia of anything, e.g. 'animal' or 'substance', clearly he has not
defined it at all: for the aforesaid terms do not differentiate anything
at all. Further, we must see whether the differentia stated possesses anything
that is co-ordinate with it in a division; for, if not, clearly the one
stated could not be a differentia of the genus. For a genus is always divided
by differentiae that are co-ordinate members of a division, as, for instance,
by the terms 'walking', 'flying', 'aquatic', and 'biped'. Or see if, though
the contrasted differentia exists, it yet is not true of the genus, for
then, clearly, neither of them could be a differentia of the genus; for
differentiae that are co-ordinates in a division with the differentia of
a thing are all true of the genus to which the thing belongs. Likewise,
also, see if, though it be true, yet the addition of it to the genus fails
to make a species. For then, clearly, this could not be a specific differentia
of the genus: for a specific differentia, if added to the genus, always
makes a species. If, however, this be no true differentia, no more is the
one adduced, seeing that it is a co-ordinate member of a division with
this.

Moreover, see if he divides the genus by a negation, as those do
who define line as 'length without breadth': for this means simply that
it has not any breadth. The genus will then be found to partake of its
own species: for, since of everything either an affirmation or its negation
is true, length must always either lack breadth or possess it, so that
'length' as well, i.e. the genus of 'line', will be either with or without
breadth. But 'length without breadth' is the definition of a species, as
also is 'length with breadth': for 'without breadth' and 'with breadth'
are differentiae, and the genus and differentia constitute the definition
of the species. Hence the genus would admit of the definition of its species.
Likewise, also, it will admit of the definition of the differentia, seeing
that one or the other of the aforesaid differentiae is of necessity predicated
of the genus. The usefulness of this principle is found in meeting those
who assert the existence of 'Ideas': for if absolute length exist, how
will it be predicable of the genus that it has breadth or that it lacks
it? For one assertion or the other will have to be true of 'length' universally,
if it is to be true of the genus at all: and this is contrary to the fact:
for there exist both lengths which have, and lengths which have not, breadth.
Hence the only people against whom the rule can be employed are those who
assert that a genus is always numerically one; and this is what is done
by those who assert the real existence of the 'Ideas'; for they allege
that absolute length and absolute animal are the genus.

It may be that in some cases the definer is obliged to employ a
negation as well, e.g. in defining privations. For 'blind' means a thing
which cannot see when its nature is to see. There is no difference between
dividing the genus by a negation, and dividing it by such an affirmation
as is bound to have a negation as its co-ordinate in a division, e.g. supposing
he had defined something as 'length possessed of breadth'; for co-ordinate
in the division with that which is possessed of breadth is that which possesses
no breadth and that only, so that again the genus is divided by a
negation.

Again, see if he rendered the species as a differentia, as do those
who define 'contumely' as 'insolence accompanied by jeering'; for jeering
is a kind of insolence, i.e. it is a species and not a
differentia.

Moreover, see if he has stated the genus as the differentia, e.g.
'Virtue is a good or noble state: for 'good' is the genus of 'virtue'.
Or possibly 'good' here is not the genus but the differentia, on the principle
that the same thing cannot be in two genera of which neither contains the
other: for 'good' does not include 'state', nor vice versa: for not every
state is good nor every good a 'state'. Both, then, could not be genera,
and consequently, if 'state' is the genus of virtue, clearly 'good' cannot
be its genus: it must rather be the differentia'. Moreover, 'a state' indicates
the essence of virtue, whereas 'good' indicates not the essence but a quality:
and to indicate a quality is generally held to be the function of the differentia.
See, further, whether the differentia rendered indicates an individual
rather than a quality: for the general view is that the differentia always
expresses a quality.

Look and see, further, whether the differentia belongs only by
accident to the object defined. For the differentia is never an accidental
attribute, any more than the genus is: for the differentia of a thing cannot
both belong and not belong to it.

Moreover, if either the differentia or the species, or any of the
things which are under the species, is predicable of the genus, then he
could not have defined the term. For none of the aforesaid can possibly
be predicated of the genus, seeing that the genus is the term with the
widest range of all. Again, see if the genus be predicated of the differentia;
for the general view is that the genus is predicated, not of the differentia,
but of the objects of which the differentia is predicated. Animal (e.g.)
is predicated of 'man' or 'ox' or other walking animals, not of the actual
differentia itself which we predicate of the species. For if 'animal' is
to be predicated of each of its differentiae, then 'animal' would be predicated
of the species several times over; for the differentiae are predicates
of the species. Moreover, the differentiae will be all either species or
individuals, if they are animals; for every animal is either a species
or an individual.

Likewise you must inquire also if the species or any of the objects
that come under it is predicated of the differentia: for this is impossible,
seeing that the differentia is a term with a wider range than the various
species. Moreover, if any of the species be predicated of it, the result
will be that the differentia is a species: if, for instance, 'man' be predicated,
the differentia is clearly the human race. Again, see if the differentia
fails to be prior to the species: for the differentia ought to be posterior
to the genus, but prior to the species.

Look and see also if the differentia mentioned belongs to a different
genus, neither contained in nor containing the genus in question. For the
general view is that the same differentia cannot be used of two non-subaltern
genera. Else the result will be that the same species as well will be in
two non-subaltern genera: for each of the differentiae imports its own
genus, e.g. 'walking' and 'biped' import with them the genus 'animal'.
If, then, each of the genera as well is true of that of which the differentia
is true, it clearly follows that the species must be in two non-subaltern
genera. Or perhaps it is not impossible for the same differentia to be
used of two non-subaltern genera, and we ought to add the words 'except
they both be subordinate members of the same genus'. Thus 'walking animal'
and 'flying animal' are non-subaltern genera, and 'biped' is the differentia
of both. The words 'except they both be subordinate members of the same
genus' ought therefore to be added; for both these are subordinate to 'animal'.
From this possibility, that the same differentia may be used of two non-subaltern
genera, it is clear also that there is no necessity for the differentia
to carry with it the whole of the genus to which it belongs, but only the
one or the other of its limbs together with the genera that are higher
than this, as 'biped' carries with it either 'flying' or 'walking
animal'.

See, too, if he has rendered 'existence in' something as the differentia
of a thing's essence: for the general view is that locality cannot differentiate
between one essence and another. Hence, too, people condemn those who divide
animals by means of the terms 'walking' and 'aquatic', on the ground that
'walking' and 'aquatic' indicate mere locality. Or possibly in this case
the censure is undeserved; for 'aquatic' does not mean 'in' anything; nor
does it denote a locality, but a certain quality: for even if the thing
be on the dry land, still it is aquatic: and likewise a land-animal, even
though it be in the water, will still be a and not an aquatic-animal. But
all the same, if ever the differentia does denote existence in something,
clearly he will have made a bad mistake.

Again, see if he has rendered an affection as the differentia:
for every affection, if intensified, subverts the essence of the thing,
while the differentia is not of that kind: for the differentia is generally
considered rather to preserve that which it differentiates; and it is absolutely
impossible for a thing to exist without its own special differentia: for
if there be no 'walking', there will be no 'man'. In fact, we may lay down
absolutely that a thing cannot have as its differentia anything in respect
of which it is subject to alteration: for all things of that kind, if intensified,
destroy its essence. If, then, a man has rendered any differentia of this
kind, he has made a mistake: for we undergo absolutely no alteration in
respect of our differentiae.

Again, see if he has failed to render the differentia of a relative
term relatively to something else; for the differentiae of relative terms
are themselves relative, as in the case also of knowledge. This is classed
as speculative, practical and productive; and each of these denotes a relation:
for it speculates upon something, and produces something and does
something.

Look and see also if the definer renders each relative term relatively
to its natural purpose: for while in some cases the particular relative
term can be used in relation to its natural purpose only and to nothing
else, some can be used in relation to something else as well. Thus sight
can only be used for seeing, but a strigil can also be used to dip up water.
Still, if any one were to define a strigil as an instrument for dipping
water, he has made a mistake: for that is not its natural function. The
definition of a thing's natural function is 'that for which it would be
used by the prudent man, acting as such, and by the science that deals
specially with that thing'.

Or see if, whenever a term happens to be used in a number of relations,
he has failed to introduce it in its primary relation: e.g. by defining
'wisdom' as the virtue of 'man' or of the 'soul,' rather than of the 'reasoning
faculty': for 'wisdom' is the virtue primarily of the reasoning faculty:
for it is in virtue of this that both the man and his soul are said to
be wise.

Moreover, if the thing of which the term defined has been stated
to be an affection or disposition, or whatever it may be, be unable to
admit it, the definer has made a mistake. For every disposition and every
affection is formed naturally in that of which it is an affection or disposition,
as knowledge, too, is formed in the soul, being a disposition of soul.
Sometimes, however, people make bad mistakes in matters of this sort, e.g.
all those who say that 'sleep' is a 'failure of sensation', or that 'perplexity'
is a state of 'equality between contrary reasonings', or that 'pain' is
a 'violent disruption of parts that are naturally conjoined'. For sleep
is not an attribute of sensation, whereas it ought to be, if it is a failure
of sensation. Likewise, perplexity is not an attribute of opposite reasonings,
nor pain of parts naturally conjoined: for then inanimate things will be
in pain, since pain will be present in them. Similar in character, too,
is the definition of 'health', say, as a 'balance of hot and cold elements':
for then health will be necessarily exhibited by the hot and cold elements:
for balance of anything is an attribute inherent in those things of which
it is the balance, so that health would be an attribute of them. Moreover,
people who define in this way put effect for cause, or cause for effect.
For the disruption of parts naturally conjoined is not pain, but only a
cause of pain: nor again is a failure of sensation sleep, but the one is
the cause of the other: for either we go to sleep because sensation fails,
or sensation fails because we go to sleep. Likewise also an equality between
contrary reasonings would be generally considered to be a cause of perplexity:
for it is when we reflect on both sides of a question and find everything
alike to be in keeping with either course that we are perplexed which of
the two we are to do.

Moreover, with regard to all periods of time look and see whether
there be any discrepancy between the differentia and the thing defined:
e.g. supposing the 'immortal' to be defined as a 'living thing immune at
present from destruction'. For a living thing that is immune 'at present'
from destruction will be immortal 'at present'. Possibly, indeed, in this
case this result does not follow, owing to the ambiguity of the words 'immune
at present from destruction': for it may mean either that the thing has
not been destroyed at present, or that it cannot be destroyed at present,
or that at present it is such that it never can be destroyed. Whenever,
then, we say that a living thing is at present immune from destruction,
we mean that it is at present a living thing of such a kind as never to
be destroyed: and this is equivalent to saying that it is immortal, so
that it is not meant that it is immortal only at present. Still, if ever
it does happen that what has been rendered according to the definition
belongs in the present only or past, whereas what is meant by the word
does not so belong, then the two could not be the same. So, then, this
commonplace rule ought to be followed, as we have said.

Part 7

You should look and see also whether the term being defined is
applied in consideration of something other than the definition rendered.
Suppose (e.g.) a definition of 'justice' as the 'ability to distribute
what is equal'. This would not be right, for 'just' describes rather the
man who chooses, than the man who is able to distribute what is equal:
so that justice could not be an ability to distribute what is equal: for
then also the most just man would be the man with the most ability to distribute
what is equal.

Moreover, see if the thing admits of degrees, whereas what is rendered
according to the definition does not, or, vice versa, what is rendered
according to the definition admits of degrees while the thing does not.
For either both must admit them or else neither, if indeed what is rendered
according to the definition is the same as the thing. Moreover, see if,
while both of them admit of degrees, they yet do not both become greater
together: e.g. suppose sexual love to be the desire for intercourse: for
he who is more intensely in love has not a more intense desire for intercourse,
so that both do not become intensified at once: they certainly should,
however, had they been the same thing.

Moreover, suppose two things to be before you, see if the term
to be defined applies more particularly to the one to which the content
of the definition is less applicable. Take, for instance, the definition
of 'fire' as the 'body that consists of the most rarefied particles'. For
'fire' denotes flame rather than light, but flame is less the body that
consists of the most rarefied particles than is light: whereas both ought
to be more applicable to the same thing, if they had been the same. Again,
see if the one expression applies alike to both the objects before you,
while the other does not apply to both alike, but more particularly to
one of them.

Moreover, see if he renders the definition relative to two things
taken separately: thus, the beautiful' is 'what is pleasant to the eyes
or to the ears": or 'the real' is 'what is capable of being acted upon
or of acting'. For then the same thing will be both beautiful and not beautiful,
and likewise will be both real and not real. For 'pleasant to the ears'
will be the same as 'beautiful', so that 'not pleasant to the ears' will
be the same as 'not beautiful': for of identical things the opposites,
too, are identical, and the opposite of 'beautiful' is 'not beautiful',
while of 'pleasant to the ears' the opposite is not pleasant to the cars':
clearly, then, 'not pleasant to the ears' is the same thing as 'not beautiful'.
If, therefore, something be pleasant to the eyes but not to the ears, it
will be both beautiful and not beautiful. In like manner we shall show
also that the same thing is both real and unreal.

Moreover, of both genera and differentiae and all the other terms
rendered in definitions you should frame definitions in lieu of the terms,
and then see if there be any discrepancy between them.

Part 8

If the term defined be relative, either in itself or in respect
of its genus, see whether the definition fails to mention that to which
the term, either in itself or in respect of its genus, is relative, e.g.
if he has defined 'knowledge' as an 'incontrovertible conception' or 'wishing'
as 'painless conation'. For of everything relative the essence is relative
to something else, seeing that the being of every relative term is identical
with being in a certain relation to something. He ought, therefore, to
have said that knowledge is 'conception of a knowable' and that wishing
is 'conation for a good'. Likewise, also, if he has defined 'grammar' as
'knowledge of letters': whereas in the definition there ought to be rendered
either the thing to which the term itself is relative, or that, whatever
it is, to which its genus is relative. Or see if a relative term has been
described not in relation to its end, the end in anything being whatever
is best in it or gives its purpose to the rest. Certainly it is what is
best or final that should be stated, e.g. that desire is not for the pleasant
but for pleasure: for this is our purpose in choosing what is pleasant
as well.

Look and see also if that in relation to which he has rendered
the term be a process or an activity: for nothing of that kind is an end,
for the completion of the activity or process is the end rather than the
process or activity itself. Or perhaps this rule is not true in all cases,
for almost everybody prefers the present experience of pleasure to its
cessation, so that they would count the activity as the end rather than
its completion.

Again see in some cases if he has failed to distinguish the quantity
or quality or place or other differentiae of an object; e.g. the quality
and quantity of the honour the striving for which makes a man ambitious:
for all men strive for honour, so that it is not enough to define the ambitious
man as him who strives for honour, but the aforesaid differentiae must
be added. Likewise, also, in defining the covetous man the quantity of
money he aims at, or in the case of the incontinent man the quality of
the pleasures, should be stated. For it is not the man who gives way to
any sort of pleasure whatever who is called incontinent, but only he who
gives way to a certain kind of pleasure. Or again, people sometimes define
night as a 'shadow on the earth', or an earthquake as a movement of the
earth', or a cloud as 'condensation of the air', or a wind as a 'movement
of the air'; whereas they ought to specify as well quantity, quality, place,
and cause. Likewise, also, in other cases of the kind: for by omitting
any differentiae whatever he fails to state the essence of the term. One
should always attack deficiency. For a movement of the earth does not constitute
an earthquake, nor a movement of the air a wind, irrespective of its manner
and the amount involved.

Moreover, in the case of conations, and in any other cases where
it applies, see if the word 'apparent' is left out, e.g. 'wishing is a
conation after the good', or 'desire is a conation after the pleasant'-instead
of saying 'the apparently good', or 'pleasant'. For often those who exhibit
the conation do not perceive what is good or pleasant, so that their aim
need not be really good or pleasant, but only apparently so. They ought,
therefore, to have rendered the definition also accordingly. On the other
hand, any one who maintains the existence of Ideas ought to be brought
face to face with his Ideas, even though he does render the word in question:
for there can be no Idea of anything merely apparent: the general view
is that an Idea is always spoken of in relation to an Idea: thus absolute
desire is for the absolutely pleasant, and absolute wishing is for the
absolutely good; they therefore cannot be for an apparent good or an apparently
pleasant: for the existence of an absolutely-apparently-good or pleasant
would be an absurdity.

Part 9

Moreover, if the definition be of the state of anything, look at
what is in the state, while if it be of what is in the state, look at the
state: and likewise also in other cases of the kind. Thus if the pleasant
be identical with the beneficial, then, too, the man who is pleased is
benefited. Speaking generally, in definitions of this sort it happens that
what the definer defines is in a sense more than one thing: for in defining
knowledge, a man in a sense defines ignorance as well, and likewise also
what has knowledge and what lacks it, and what it is to know and to be
ignorant. For if the first be made clear, the others become in a certain
sense clear as well. We have, then, to be on our guard in all such cases
against discrepancy, using the elementary principles drawn from consideration
of contraries and of coordinates.

Moreover, in the case of relative terms, see if the species is
rendered as relative to a species of that to which the genus is rendered
as relative, e.g. supposing belief to be relative to some object of belief,
see whether a particular belief is made relative to some particular object
of belief: and, if a multiple be relative to a fraction, see whether a
particular multiple be made relative to a particular fraction. For if it
be not so rendered, clearly a mistake has been made.

See, also, if the opposite of the term has the opposite definition,
whether (e.g.) the definition of 'half' is the opposite of that of 'double':
for if 'double' is 'that which exceeds another by an equal amount to that
other', 'half' is 'that which is exceeded by an amount equal to itself'.
In the same way, too, with contraries. For to the contrary term will apply
the definition that is contrary in some one of the ways in which contraries
are conjoined. Thus (e.g.) if 'useful'='productive of good', 'injurious'=productive
of evil' or 'destructive of good', for one or the other of thee is bound
to be contrary to the term originally used. Suppose, then, neither of these
things to be the contrary of the term originally used, then clearly neither
of the definitions rendered later could be the definition of the contrary
of the term originally defined: and therefore the definition originally
rendered of the original term has not been rightly rendered either. Seeing,
moreover, that of contraries, the one is sometimes a word forced to denote
the privation of the other, as (e.g.) inequality is generally held to be
the privation of equality (for 'unequal' merely describes things that are
not equal'), it is therefore clear that that contrary whose form denotes
the privation must of necessity be defined through the other; whereas the
other cannot then be defined through the one whose form denotes the privation;
for else we should find that each is being interpreted by the other. We
must in the case of contrary terms keep an eye on this mistake, e.g. supposing
any one were to define equality as the contrary of inequality: for then
he is defining it through the term which denotes privation of it. Moreover,
a man who so defines is bound to use in his definition the very term he
is defining; and this becomes clear, if for the word we substitute its
definition. For to say 'inequality' is the same as to say 'privation of
equality'. Therefore equality so defined will be 'the contrary of the privation
of equality', so that he would have used the very word to be defined. Suppose,
however, that neither of the contraries be so formed as to denote privation,
but yet the definition of it be rendered in a manner like the above, e.g.
suppose 'good' to be defined as 'the contrary of evil', then, since it
is clear that 'evil' too will be 'the contrary of good' (for the definition
of things that are contrary in this must be rendered in a like manner),
the result again is that he uses the very term being defined: for 'good'
is inherent in the definition of 'evil'. If, then, 'good' be the contrary
of evil, and evil be nothing other than the 'contrary of good', then 'good'
will be the 'contrary of the contrary of good'. Clearly, then, he has used
the very word to be defined.

Moreover, see if in rendering a term formed to denote privation,
he has failed to render the term of which it is the privation, e.g. the
state, or contrary, or whatever it may be whose privation it is: also if
he has omitted to add either any term at all in which the privation is
naturally formed, or else that in which it is naturally formed primarily,
e.g. whether in defining 'ignorance' a privation he has failed to say that
it is the privation of 'knowledge'; or has failed to add in what it is
naturally formed, or, though he has added this, has failed to render the
thing in which it is primarily formed, placing it (e.g.) in 'man' or in
'the soul', and not in the 'reasoning faculty': for if in any of these
respects he fails, he has made a mistake. Likewise, also, if he has failed
to say that 'blindness' is the 'privation of sight in an eye': for a proper
rendering of its essence must state both of what it is the privation and
what it is that is deprived.

Examine further whether he has defined by the expression 'a privation'
a term that is not used to denote a privation: thus a mistake of this sort
also would be generally thought to be incurred in the case of 'error' by
any one who is not using it as a merely negative term. For what is generally
thought to be in error is not that which has no knowledge, but rather that
which has been deceived, and for this reason we do not talk of inanimate
things or of children as 'erring'. 'Error', then, is not used to denote
a mere privation of knowledge.

Part 10

Moreover, see whether the like inflexions in the definition apply
to the like inflexions of the term; e.g. if 'beneficial' means 'productive
of health', does 'beneficially' mean productively of health' and a 'benefactor'
a 'producer of health'?

Look too and see whether the definition given will apply to the
Idea as well. For in some cases it will not do so; e.g. in the Platonic
definition where he adds the word 'mortal' in his definitions of living
creatures: for the Idea (e.g. the absolute Man) is not mortal, so that
the definition will not fit the Idea. So always wherever the words 'capable
of acting on' or 'capable of being acted upon' are added, the definition
and the Idea are absolutely bound to be discrepant: for those who assert
the existence of Ideas hold that they are incapable of being acted upon,
or of motion. In dealing with these people even arguments of this kind
are useful.

Further, see if he has rendered a single common definition of terms
that are used ambiguously. For terms whose definition corresponding their
common name is one and the same, are synonymous; if, then, the definition
applies in a like manner to the whole range of the ambiguous term, it is
not true of any one of the objects described by the term. This is, moreover,
what happens to Dionysius' definition of 'life' when stated as 'a movement
of a creature sustained by nutriment, congenitally present with it': for
this is found in plants as much as in animals, whereas 'life' is generally
understood to mean not one kind of thing only, but to be one thing in animals
and another in plants. It is possible to hold the view that life is a synonymous
term and is always used to describe one thing only, and therefore to render
the definition in this way on purpose: or it may quite well happen that
a man may see the ambiguous character of the word, and wish to render the
definition of the one sense only, and yet fail to see that he has rendered
a definition common to both senses instead of one peculiar to the sense
he intends. In either case, whichever course he pursues, he is equally
at fault. Since ambiguous terms sometimes pass unobserved, it is best in
questioning to treat such terms as though they were synonymous (for the
definition of the one sense will not apply to the other, so that the answerer
will be generally thought not to have defined it correctly, for to a synonymous
term the definition should apply in its full range), whereas in answering
you should yourself distinguish between the senses. Further, as some answerers
call 'ambiguous' what is really synonymous, whenever the definition rendered
fails to apply universally, and, vice versa, call synonymous what is really
ambiguous supposing their definition applies to both senses of the term,
one should secure a preliminary admission on such points, or else prove
beforehand that so-and-so is ambiguous or synonymous, as the case may be:
for people are more ready to agree when they do not foresee what the consequence
will be. If, however, no admission has been made, and the man asserts that
what is really synonymous is ambiguous because the definition he has rendered
will not apply to the second sense as well, see if the definition of this
second meaning applies also to the other meanings: for if so, this meaning
must clearly be synonymous with those others. Otherwise, there will be
more than one definition of those other meanings, for there are applicable
to them two distinct definitions in explanation of the term, viz. the one
previously rendered and also the later one. Again, if any one were to define
a term used in several senses, and, finding that his definition does not
apply to them all, were to contend not that the term is ambiguous, but
that even the term does not properly apply to all those senses, just because
his definition will not do so either, then one may retort to such a man
that though in some things one must not use the language of the people,
yet in a question of terminology one is bound to employ the received and
traditional usage and not to upset matters of that sort.

Part 11

Suppose now that a definition has been rendered of some complex
term, take away the definition of one of the elements in the complex, and
see if also the rest of the definition defines the rest of it: if not,
it is clear that neither does the whole definition define the whole complex.
Suppose, e.g. that some one has defined a 'finite straight line' as 'the
limit of a finite plane, such that its centre is in a line with its extremes';
if now the definition of a finite line' be the 'limit of a finite plane',
the rest (viz. 'such that its centre is in a line with its extremes') ought
to be a definition of straight'. But an infinite straight line has neither
centre nor extremes and yet is straight so that this remainder does not
define the remainder of the term.

Moreover, if the term defined be a compound notion, see if the
definition rendered be equimembral with the term defined. A definition
is said to be equimembral with the term defined when the number of the
elements compounded in the latter is the same as the number of nouns and
verbs in the definition. For the exchange in such cases is bound to be
merely one of term for term, in the case of some if not of all, seeing
that there are no more terms used now than formerly; whereas in a definition
terms ought to be rendered by phrases, if possible in every case, or if
not, in the majority. For at that rate, simple objects too could be defined
by merely calling them by a different name, e.g. 'cloak' instead of
'doublet'.

The mistake is even worse, if actually a less well known term be
substituted, e.g. 'pellucid mortal' for 'white man': for it is no definition,
and moreover is less intelligible when put in that form.

Look and see also whether, in the exchange of words, the sense
fails still to be the same. Take, for instance, the explanation of 'speculative
knowledge' as 'speculative conception': for conception is not the same
as knowledge-as it certainly ought to be if the whole is to be the same
too: for though the word 'speculative' is common to both expressions, yet
the remainder is different.

Moreover, see if in replacing one of the terms by something else
he has exchanged the genus and not the differentia, as in the example just
given: for 'speculative' is a less familiar term than knowledge; for the
one is the genus and the other the differentia, and the genus is always
the most familiar term of all; so that it is not this, but the differentia,
that ought to have been changed, seeing that it is the less familiar. It
might be held that this criticism is ridiculous: because there is no reason
why the most familiar term should not describe the differentia, and not
the genus; in which case, clearly, the term to be altered would also be
that denoting the genus and not the differentia. If, however, a man is
substituting for a term not merely another term but a phrase, clearly it
is of the differentia rather than of the genus that a definition should
be rendered, seeing that the object of rendering the definition is to make
the subject familiar; for the differentia is less familiar than the
genus.

If he has rendered the definition of the differentia, see whether
the definition rendered is common to it and something else as well: e.g.
whenever he says that an odd number is a 'number with a middle', further
definition is required of how it has a middle: for the word 'number' is
common to both expressions, and it is the word 'odd' for which the phrase
has been substituted. Now both a line and a body have a middle, yet they
are not 'odd'; so that this could not be a definition of 'odd'. If, on
the other hand, the phrase 'with a middle' be used in several senses, the
sense here intended requires to be defined. So that this will either discredit
the definition or prove that it is no definition at
all.

Part 12

Again, see if the term of which he renders the definition is a
reality, whereas what is contained in the definition is not, e.g. Suppose
'white' to be defined as 'colour mingled with fire': for what is bodiless
cannot be mingled with body, so that 'colour' 'mingled with fire' could
not exist, whereas 'white' does exist.

Moreover, those who in the case of relative terms do not distinguish
to what the object is related, but have described it only so as to include
it among too large a number of things, are wrong either wholly or in part;
e.g. suppose some one to have defined 'medicine' as a science of Reality'.
For if medicine be not a science of anything that is real, the definition
is clearly altogether false; while if it be a science of some real thing,
but not of another, it is partly false; for it ought to hold of all reality,
if it is said to be of Reality essentially and not accidentally: as is
the case with other relative terms: for every object of knowledge is a
term relative to knowledge: likewise, also, with other relative terms,
inasmuch as all such are convertible. Moreover, if the right way to render
account of a thing be to render it as it is not in itself but accidentally,
then each and every relative term would be used in relation not to one
thing but to a number of things. For there is no reason why the same thing
should not be both real and white and good, so that it would be a correct
rendering to render the object in relation to any one whatsoever of these,
if to render what it is accidentally be a correct way to render it. It
is, moreover, impossible that a definition of this sort should be peculiar
to the term rendered: for not only but the majority of the other sciences
too, have for their object some real thing, so that each will be a science
of reality. Clearly, then, such a definition does not define any science
at all; for a definition ought to be peculiar to its own term, not
general.

Sometimes, again, people define not the thing but only the thing
in a good or perfect condition. Such is the definition of a rhetorician
as 'one who can always see what will persuade in the given circumstances,
and omit nothing'; or of a thief, as 'one who pilfers in secret': for clearly,
if they each do this, then the one will be a good rhetorician, and the
other a good thief: whereas it is not the actual pilfering in secret, but
the wish to do it, that constitutes the thief.

Again, see if he has rendered what is desirable for its own sake
as desirable for what it produces or does, or as in any way desirable because
of something else, e.g. by saying that justice is 'what preserves the laws'
or that wisdom is 'what produces happiness'; for what produces or preserves
something else is one of the things desirable for something else. It might
be said that it is possible for what is desirable in itself to be desirable
for something else as well: but still to define what is desirable in itself
in such a way is none the less wrong: for the essence contains par excellence
what is best in anything, and it is better for a thing to be desirable
in itself than to be desirable for something else, so that this is rather
what the definition too ought to have indicated.

Part 13

See also whether in defining anything a man has defined it as an
'A and B', or as a 'product of A and B' or as an 'A+B'. If he defines it
as and B', the definition will be true of both and yet of neither of them;
suppose, e.g. justice to be defined as 'temperance and courage.' For if
of two persons each has one of the two only, both and yet neither will
be just: for both together have justice, and yet each singly fails to have
it. Even if the situation here described does not so far appear very absurd
because of the occurrence of this kind of thing in other cases also (for
it is quite possible for two men to have a mina between them, though neither
of them has it by himself), yet least that they should have contrary attributes
surely seems quite absurd; and yet this will follow if the one be temperate
and yet a coward, and the other, though brave, be a profligate; for then
both will exhibit both justice and injustice: for if justice be temperance
and bravery, then injustice will be cowardice and profligacy. In general,
too, all the ways of showing that the whole is not the same as the sum
of its parts are useful in meeting the type just described; for a man who
defines in this way seems to assert that the parts are the same as the
whole. The arguments are particularly appropriate in cases where the process
of putting the parts together is obvious, as in a house and other things
of that sort: for there, clearly, you may have the parts and yet not have
the whole, so that parts and whole cannot be the same.

If, however, he has said that the term being defined is not 'A
and B' but the 'product of A and B', look and see in the first place if
A and B cannot in the nature of things have a single product: for some
things are so related to one another that nothing can come of them, e.g.
a line and a number. Moreover, see if the term that has been defined is
in the nature of things found primarily in some single subject, whereas
the things which he has said produce it are not found primarily in any
single subject, but each in a separate one. If so, clearly that term could
not be the product of these things: for the whole is bound to be in the
same things wherein its parts are, so that the whole will then be found
primarily not in one subject only, but in a number of them. If, on the
other hand, both parts and whole are found primarily in some single subject,
see if that medium is not the same, but one thing in the case of the whole
and another in that of the parts. Again, see whether the parts perish together
with the whole: for it ought to happen, vice versa, that the whole perishes
when the parts perish; when the whole perishes, there is no necessity that
the parts should perish too. Or again, see if the whole be good or evil,
and the parts neither, or, vice versa, if the parts be good or evil and
the whole neither. For it is impossible either for a neutral thing to produce
something good or bad, or for things good or bad to produce a neutral thing.
Or again, see if the one thing is more distinctly good than the other is
evil, and yet the product be no more good than evil, e.g. suppose shamelessness
be defined as 'the product of courage and false opinion': here the goodness
of courage exceeds the evil of false opinion; accordingly the product of
these ought to have corresponded to this excess, and to be either good
without qualification, or at least more good than evil. Or it may be that
this does not necessarily follow, unless each be in itself good or bad;
for many things that are productive are not good in themselves, but only
in combination; or, per contra, they are good taken singly, and bad or
neutral in combination. What has just been said is most clearly illustrated
in the case of things that make for health or sickness; for some drugs
are such that each taken alone is good, but if they are both administered
in a mixture, bad.

Again, see whether the whole, as produced from a better and worse,
fails to be worse than the better and better than the worse element. This
again, however, need not necessarily be the case, unless the elements compounded
be in themselves good; if they are not, the whole may very well not be
good, as in the cases just instanced.

Moreover, see if the whole be synonymous with one of the elements:
for it ought not to be, any more than in the case of syllables: for the
syllable is not synonymous with any of the letters of which it is made
up.

Moreover, see if he has failed to state the manner of their composition:
for the mere mention of its elements is not enough to make the thing intelligible.
For the essence of any compound thing is not merely that it is a product
of so-and-so, but that it is a product of them compounded in such and such
a way, just as in the case of a house: for here the materials do not make
a house irrespective of the way they are put together.

If a man has defined an object as 'A+B', the first thing to be
said is that 'A+B' means the same either as 'A and B', or as the 'product
of A and B.' for 'honey+water' means either the honey and the water, or
the 'drink made of honey and water'. If, then, he admits that 'A+B' is
+ B' is the same as either of these two things, the same criticisms will
apply as have already been given for meeting each of them. Moreover, distinguish
between the different senses in which one thing may be said to be '+' another,
and see if there is none of them in which A could be said to exist '+ B.'
Thus e.g. supposing the expression to mean that they exist either in some
identical thing capable of containing them (as e.g. justice and courage
are found in the soul), or else in the same place or in the same time,
and if this be in no way true of the A and B in question, clearly the definition
rendered could not hold of anything, as there is no possible way in which
A can exist B'. If, however, among the various senses above distinguished,
it be true that A and B are each found in the same time as the other, look
and see if possibly the two are not used in the same relation. Thus e.g.
suppose courage to have been defined as 'daring with right reasoning':
here it is possible that the person exhibits daring in robbery, and right
reasoning in regard to the means of health: but he may have 'the former
quality+the latter' at the same time, and not as yet be courageous! Moreover,
even though both be used in the same relation as well, e.g. in relation
to medical treatment (for a man may exhibit both daring and right reasoning
in respect of medical treatment), still, none the less, not even this combination
of 'the one+the other 'makes him 'courageous'. For the two must not relate
to any casual object that is the same, any more than each to a different
object; rather, they must relate to the function of courage, e.g. meeting
the perils of war, or whatever is more properly speaking its function than
this.

Some definitions rendered in this form fail to come under the aforesaid
division at all, e.g. a definition of anger as 'pain with a consciousness
of being slighted'. For what this means to say is that it is because of
a consciousness of this sort that the pain occurs; but to occur 'because
of' a thing is not the same as to occur '+ a thing' in any of its aforesaid
senses.

Part 14

Again, if he have described the whole compounded as the 'composition'
of these things (e.g. 'a living creature' as a 'composition of soul and
body'), first of all see whether he has omitted to state the kind of composition,
as (e.g.) in a definition of 'flesh' or 'bone' as the 'composition of fire,
earth, and air'. For it is not enough to say it is a composition, but you
should also go on to define the kind of composition: for these things do
not form flesh irrespective of the manner of their composition, but when
compounded in one way they form flesh, when in another, bone. It appears,
moreover, that neither of the aforesaid substances is the same as a 'composition'
at all: for a composition always has a decomposition as its contrary, whereas
neither of the aforesaid has any contrary. Moreover, if it is equally probable
that every compound is a composition or else that none is, and every kind
of living creature, though a compound, is never a composition, then no
other compound could be a composition either.

Again, if in the nature of a thing two contraries are equally liable
to occur, and the thing has been defined through the one, clearly it has
not been defined; else there will be more than one definition of the same
thing; for how is it any more a definition to define it through this one
than through the other, seeing that both alike are naturally liable to
occur in it? Such is the definition of the soul, if defined as a substance
capable of receiving knowledge: for it has a like capacity for receiving
ignorance.

Also, even when one cannot attack the definition as a whole for
lack of acquaintance with the whole, one should attack some part of it,
if one knows that part and sees it to be incorrectly rendered: for if the
part be demolished, so too is the whole definition. Where, again, a definition
is obscure, one should first of all correct and reshape it in order to
make some part of it clear and get a handle for attack, and then proceed
to examine it. For the answerer is bound either to accept the sense as
taken by the questioner, or else himself to explain clearly whatever it
is that his definition means. Moreover, just as in the assemblies the ordinary
practice is to move an emendation of the existing law and, if the emendation
is better, they repeal the existing law, so one ought to do in the case
of definitions as well: one ought oneself to propose a second definition:
for if it is seen to be better, and more indicative of the object defined,
clearly the definition already laid down will have been demolished, on
the principle that there cannot be more than one definition of the same
thing.

In combating definitions it is always one of the chief elementary
principles to take by oneself a happy shot at a definition of the object
before one, or to adopt some correctly expressed definition. For one is
bound, with the model (as it were) before one's eyes, to discern both any
shortcoming in any features that the definition ought to have, and also
any superfluous addition, so that one is better supplied with lines of
attack.